Ride performance optimization in an active suspension system

ABSTRACT

An active vehicle suspension system includes an active damping mechanism operatively coupled to a vehicle wheel and configured for controlling a damping force applied to the wheel responsive to a control signal. A controller is operatively coupled to the damping mechanism and configured for generating a control signal to the damping mechanism responsive to velocity of the wheel in a downward vertical direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/531,997,filed Jun. 25, 2012, the content of which is incorporated herein byreference in its entirety.

BACKGROUND

The embodiments of the present disclosure relate to active vehiclesuspension systems incorporating continuously variable or multistepsuspension dampers, and to methods for controlling such systems.

Vehicles may incorporate active or adaptive suspension systems toactively control the vertical movements of the vehicle wheels ratherthan allowing such movements to be determined entirely by interactionswith the road surface. In order to maximize ride comfort in suchvehicles, it is usually desirable to maintain the damping levels invehicle shock absorbers at a relatively low value.

However, when a vehicle wheel encounters a depression (such as apothole) in the road surface, a lower damping level permits the wheel tofall relatively rapidly into the pothole. Generally, the deeper thewheel falls into the hole, the greater the impact forces generated bythe wheel impacting a far side of the hole just prior to rising out ofthe hole. With the wheel damping level at a relatively low value, theseimpact forces are transmitted through the vehicle suspension to theremainder of the vehicle, adversely affecting ride quality.

While increasing the level of wheel damping would reduce the impactforces transmitted to the vehicle and suspension, this would adverselyaffect ride quality when the vehicle is traveling on a normal, levelroad surface. Thus, it is desirable to increase damping levels only whena pothole is encountered, while maintaining the damping levels at therelatively lower value when the wheel is riding on a level road surface.

SUMMARY

In one aspect of the embodiments of the present disclosure, an activevehicle suspension system is provided including an active dampingmechanism operatively coupled to a vehicle wheel and configured forcontrolling a damping force applied to the wheel responsive to a controlsignal. A controller is operatively coupled to the damping mechanism andconfigured for generating a control signal to the damping mechanismresponsive to a velocity of the wheel in a downward vertical direction.

In another aspect of the embodiments of the present disclosure, a methodis provided for controlling a vehicle suspension for a wheel via acontroller. The method includes repeatedly calculating a verticalvelocity of the wheel until the vertical velocity exceeds a firstvelocity threshold; in response to the vertical velocity exceeding thefirst velocity threshold, initiating a timer and maintaining a dampinglevel of an adjustable damping mechanism of the vehicle suspension at aninitial value while repeatedly recalculating the vertical velocity ofthe wheel until the recalculated vertical velocity exceeds a secondvelocity threshold; and in response to the recalculated verticalvelocity exceeding the second velocity threshold before the timerexceeds a first time threshold, sending an adjustment signal to theadjustable damping mechanism of the vehicle suspension to increase thedamping level of the suspension.

In another aspect of the embodiments of the present disclosure, avehicle suspension system is provided, the system including an activedamping mechanism operatively coupled to a vehicle wheel and configuredto control damping applied to the wheel, and a controller operativelycoupled to the active damping mechanism. The controller is configuredto: repeatedly calculate a vertical velocity of the wheel until thevertical velocity exceeds a first velocity threshold; in response to thevertical velocity exceeding the first velocity threshold, initiate atimer and maintain a damping level of the active damping mechanism at aninitial value of damping while repeatedly recalculating the verticalvelocity of the wheel until the recalculated vertical velocity exceeds asecond velocity threshold; and in response to the recalculated verticalvelocity exceeding the second velocity threshold before the timerexceeds a first time threshold, adjust the active damping mechanism toincrease the damping level applied to the wheel.

In another aspect of the embodiments of the present disclosure, a methodis provided for controlling a damping level applied to a wheel in anactive suspension system. The method includes the steps of determining avelocity defined as a rate of change of a vertical position of the wheelover a first predetermined time period; comparing the velocity to avelocity threshold; and where the velocity is greater than thevelocity-threshold, increasing the damping level.

In another aspect of the embodiments of the present disclosure, a methodis provided for applying a damping force to a wheel moving in a downwardvertical direction. The method includes the steps of measuring a timeduring which the wheel moves in the direction; measuring a velocity ofthe wheel in the direction; comparing the time to a threshold and thevelocity to another threshold; and where the time does not exceed thethreshold and the velocity exceeds the other threshold, applying amaximum available damping force to the wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a portion of an active vehiclesuspension system suitable for implementing a damping force controlroutine in accordance with an embodiment of the present disclosure.

FIG. 2 is a block diagram of an exemplary adjustable damping mechanismcontrollable in accordance with a damping force control routine inaccordance with an embodiment of the present disclosure.

FIG. 3 is a block diagram showing a flow of a damping force controlroutine for controlling forces in the active damping mechanisms

FIG. 4 is a block diagram showing a vehicle wheel moving along a roadsurface prior to entering a pothole or other depression in the roadsurface.

FIG. 5 is a block diagram showing a vehicle wheel moving along a roadsurface after entering a pothole or other depression in the roadsurface.

DETAILED DESCRIPTION

FIG. 1 shows a schematic representation of a portion of one embodimentof an active vehicle suspension system (generally designated 10)configured for controlling damping forces provided by damping mechanisms(for example, shock absorbers) of the vehicle suspension. The activevehicle suspension system includes such active damping mechanismsoperatively coupled to associated wheels of the vehicle. These dampingmechanisms are configured for controlling a damping force applied to thewheel responsive to control signals generated by a computer processor.The computer may be incorporated into a suspension system controller 40forming part of an overall vehicle system control system (not shown).

The active suspension system 10 incorporates an embodiment of a dampinglevel control routine as described herein, which is usable forcontrolling the damping forces responsive to an interaction between avehicle wheel supported by the damping element and a depression in aroad surface on which the wheel is rolling. Spring elements and variousother elements of a conventional active vehicle suspension system mayalso be incorporated in system 10, but are not shown in FIG. 1.

In the embodiment shown in FIG. 1, suspension system 10 includes wheelposition sensors 12 (indicated by 12-1, 12-2, 12-3, and 12-4)operatively coupled to a corresponding one of each of vehicle wheels20-1, 20-2, 20-3, 20-4 and also to controller 40. Sensor(s) 12 areconfigured for detecting the vertical position of the correspondingvehicle wheel (i.e., the component of the wheel motion along a verticalor “y”-axis 333 extending through the wheel center) and with respect toa reference location in relation to which the wheel is movable. In oneembodiment, the reference location is a location on a chassis 22 of thevehicle. In one embodiment, signals representative of wheel position yare continuously received from sensors 12 by a microcomputer 30 forprocessing in a manner described below.

In the embodiment shown in FIG. 1, suspension system 10 also includes amicrocomputer 30 operatively coupled to sensors 12 and configured forprocessing signals indicating the wheel location in accordance with thecontrol routine to generate control signals used to control the dampinglevels in the adjustable damping mechanism operatively coupled to eachwheel. The computer 30 is configured to determine the vertical velocityof the wheel as the wheel interacts with the road surface. In oneembodiment, the vertical velocity of the wheel is determined by takingthe time derivative (dy/dt) of the wheel position over a predeterminedtime period. In another embodiment, the vertical velocity of the wheelis determined by integrating a value provided, for example, by anaccelerometer configured to measure the rate of change in velocity ofthe wheel in a vertical direction. Computer 30 may include a memory forstoring the damping level control routine and any additional data orprograms that may be required for operation of the suspension system.Computer 30 is incorporated into or operatively coupled to thesuspension controller 40.

If desired, one or more known filters 32 (for example, band-passfilters) may be operatively coupled to sensors 12 for filtering noisecomponents from the sensor signals in a known manner. In addition, apre-processing circuit 34 may be operatively coupled to sensors 12 ifneeded, for converting signals received from the sensors 12 into a formsuitable for processing by computer 30. If required, control signalsgenerated by microcomputer 30 may be transmitted to a driving circuit orpost-processor 36 for conversion to a form to which the adjustabledamping mechanisms 18 are responsive. The driving circuit may beconfigured to process the received control signals into a form suitablefor operating hydraulically-actuated cylinders, cylinders actuated bysolenoid valves or electromagnetically energized proportional-actionvalves, cylinders incorporating a magneto-rheological fluid, or anyother suitable types of active cylinders or shock-absorbers, forexample.

A timer element 50 is also incorporated into or operatively coupled tocontroller 40. Timer 50 is used in the manner described below to measurethe lengths of various time periods during which the vertical positionof the vehicle wheel is changing as the wheel falls into a depression inthe road surface.

If desired, any elements (for example, computer 30, filter 32, etc.)needed to interface between the sensors 12 and the active dampingmechanisms may be incorporated into a suspension controller operativelycoupled to the damping mechanisms and configured for generating controlsignals to the damping mechanisms. As previously described, thecontroller controls adjustment of the damping levels by receiving thesensor signals and generating appropriate control commands to the activedamping mechanisms 18.

Referring to FIGS. 1 and 2, the suspension system 10 includes anindependently operable, active damping mechanism 18 operatively coupledto each vehicle wheel between an unsprung mass and a sprung mass of thevehicle. The damping mechanism 18 coupled to each wheel is operableindependently of the damping mechanisms 18 coupled to the other wheels.

FIG. 2 shows one particular structure of an adjustable damping mechanismcontrollable by controller 40 for implementing embodiments of thedamping force control routine described herein. Referring to FIGS. 1 and2, each of damping mechanisms 18-1, 18-2, 18-3, and 18-4 includes anassociated shock absorber which is provided between an unsprung mass anda sprung mass of the vehicle. Each shock absorber includes a hydrauliccylinder 12 subdivided by a piston 11 into an upper and a lower fluidchamber and supported on the unsprung mass of the vehicle. A piston rod13 of piston 11 is carried by the sprung mass of the vehicle. The upperand lower fluid chambers of the hydraulic cylinder 12 are interconnectedthrough a variable orifice 14. The opening size of the variable orifice14 is controlled by operation of an associated stepping motor 15 tocontrol the damping force of the shock absorber. In the embodiment shownin FIG. 2, at each of adjustable damping mechanisms 18, the steppingmotor 15 is driven to control the size of an associated variable orifice14 to control the damping force provided by the shock absorbers inadjustable damping mechanisms 18. Thus, in this embodiment, the drivingcircuit 36 drives each of the stepping motors 15 in response to controlsignals received from computer 30. The lower fluid chamber of thehydraulic cylinder 12 is connected to an associated gas spring unit 16which is provided to absorb the volume change in the lower fluid chambercaused by movement of the piston rod 13.

As stated previously, instead of units utilizing stepping motors tocontrol the damping force of the shock absorber, adjustable dampingmechanisms 18 in accordance with embodiments of the present disclosuremay include hydraulically-actuated cylinders, cylinders actuated bysolenoid valves or electromagnetically energized proportional-actionvalves, cylinders incorporating a magneto-rheological fluid, or anyother suitable types of cylinders or shock-absorbers, for example.However, each adjustable damping mechanism 18 may be of any known typecontrollable by the methods and components described herein to adjustthe damping force applied to an associated wheel, and capable of thedynamic response required to provide the variations in damping levelsdescribed herein.

In the embodiments of the present disclosure, the computer 30 isdesigned to repeatedly execute the control routine shown in the flowdiagram of FIG. 3. Thus, hereinafter, control of a damping force whichattenuates vertical motion of the wheel relative to the vehicle body atthe right front road wheel will be described with reference to FIG. 3.

Assuming that the computer 30 has been connected to an electric powersource (not shown) by operation of an ignition switch (not shown) of thevehicle, the computer 30 initializes the control program of FIG. 3 andrepeats execution of processing steps 290-320 of the program.

FIG. 3 shows one embodiment of a control routine for the portion of theactive suspension system controlling the damping level applied to asingle wheel 20 of the vehicle. It will be understood that this samecontrol routine may be applied independently to any of the wheels of thevehicle, responsive to the road conditions experienced by the respectivewheel.

The control routine controls the damping force applied to the wheelresponsive to a protocol activated when the time rate of change of thevertical position of the wheel indicates that the wheel may haveencountered a pothole or other depression in the road surface. In FIGS.4 and 5, the parameter “y” represents a current position of the wheel 20along a vertical axis with respect to a predetermined reference location(for example, a location on the chassis 90) with respect to which thewheel is movable vertically, and parameter D represents a damping forcelevel applied to the wheel. Arrow “A” represents the direction ofvehicle travel along road surface 902.

In block 290 of the control routine, parameters y and D are at initiallevels representing a state of an associated damping element 18 prior tothe wheel 20 encountering a chuck hole or pothole 900. FIG. 4 also showsthe wheel 20 moving along the road surface 902 prior to entering thepothole 900. Initially, the wheel 20 is traveling along a relativelysmooth portion of the road 902, and the elements of the suspensionsystem are adjusted so as to provide a damping level D having an initial(i.e., “normal”) reference value of D1. The initial value of D1 may beany desired value within the controllable range of settings for thedamping level D, depending on the specific characteristics and elementsof the particular suspension system. In the embodiments of the presentdisclosure described herein, the initial damping level D1 is set toprovide a relatively low degree of damping to the wheel motion, therebyproviding a relatively “softer” suspension for enhanced ride quality. Inaddition, the vertical position y1 of the wheel with respect to thereference location while the wheel is travelling along the smooth roadsurface is assigned a “0” (zero) value.

At block 300 of FIG. 3 and as shown in FIG. 5, the wheel 20 hasencountered a relative depression 900 in the road 902 which may or maynot be a pothole. As a result of the depression 900, road support isremoved from the wheel 20 and the wheel begins to drop into thedepression. Position sensor 12 operatively coupled to the wheelcontinuously senses the vertical wheel position “y” as the wheel dropsinto the depression and conveys this position to computer 30.

In the manner previously described, after passage of a predeterminedtime interval Δt, the new, lower position of the wheel is assigned tothe variable y2 by the computer. The computer 30 then calculates theabsolute value of the time rate of change in position Δy₁=y2−y1 of thewheel over the predetermined time interval Δt (i.e., the computercalculates the time derivative of position coordinate y, which is(dy/dt). This calculated time rate of change in wheel position isassigned to the variable V, and represents the instantaneous velocity ofthe wheel in the vertical direction at time Δt and in wheel position y2.For purposes of adjusting the damping forces applied to the wheel, thecontemplated range of values of Δt includes values less than 10milliseconds. In one particular embodiment, the value of Δt is 2milliseconds. The range of values of Δt depends on type of suspensiondesign and components used and other pertinent factors. However, thevalue of Δt may be set at any desired value, depending on therequirements of a particular application. As stated previously, thepredetermined value of Δt may be stored, for example, in a look-up tablein computer memory. In general, for purposes of adjusting the dampingforces applied to the wheel, it is desirable that the time interval Δtbe as short as possible so that a rapid determination can be maderegarding whether the threshold value Th1 has been exceeded and further,rapid successive measurements of the wheel position y are required.

In block 302, the calculated value of the instantaneous velocity V iscompared to a first predetermined velocity threshold value Th1. If V isless than Th1, a “false” condition is recognized and the process returnsto block 290 (i.e., the damping level D is maintained at the initialreference value of D1). This damping level is maintained until the wheelencounters a depression in the road. However, if V is equal to orexceeds Th1, a “true” condition is recognized. The fact that theinstantaneous velocity V met or exceeded the threshold value Th1 istaken as an indication that the wheel is potentially beginning to fallinto a depression 900. The satisfaction of this condition is interpretedas confirmation that the wheel has encountered a potential potholecondition and, following this confirmation, the “y” position of thewheel is measured at very short intervals of time to monitor thecontinued drop (if any) of the wheel into the depression. The occurrenceof a “true” condition indicates that the change in wheel position (Δy)over the elapsed time Δt (i.e., the speed of the vertical component ofmotion of the wheel into the depression) as just measured is sufficientto warrant initialization and activation of timer 50 to measure the timeelapsed during any further changes in wheel position. In this case, theprocess goes to block 304.

The predetermined velocity threshold values used by the control routineas described herein may be stored, for example, in a look-up table incomputer memory. The predetermined velocity threshold values may becalculated and/or iteratively determined by experimentation for eachconfiguration of a wheel and an associated active suspension system, andthen saved in the computer memory. The predetermined velocity thresholdvalues are selected with a view to minimizing the deleterious effects onride and maximizing the probability of detecting an actual pothole eventas soon as possible upon its occurrence. Values typically range between0.2 meters/second and 5 meters/second. Factors affecting the range ofvalues include suspension tuning, vehicle speed, vehicle tirecharacteristics, and other factors. The ranges of values for the variousvelocity thresholds may be based on data collected from both potholesand non-pothole ride events. The use of such data to program or “tune”the suspension system facilitates rapid detection of actual potholes,while helping to minimize negative effects on ride due to increases indamping prompted by “false positive” detections of pothole events.

At block 304, once it has been determined that the wheel may haveencountered a pothole event, the timer is set to an initial value ofT=0, and then allowed to increment.

The loop or subroutine formed by blocks 305, 306 and 308 is directed tocomparing the instantaneous velocity V of the wheel at successive pointsin time to another predetermined threshold velocity value Th2 untileither (1) the timer value T exceeds a predetermined first timethreshold T1, or (2) the instantaneous velocity V of the wheel exceedsthe predetermined velocity threshold value Th2. As before, theinstantaneous velocities V at the successive points in time arecalculated by taking the time derivative of the vertical position y ofthe wheel (dy/dt) where dt is the time elapsed between any two thesuccessive points in time at which the wheel location y is measured anddy is the additional vertical distance the wheel has fallen during thetime dt. In the embodiments described herein, the range of values for T1is 0.001 to 0.100 milliseconds. Generally, the time threshold T1 islonger than the value of Δt. The length of T1 should be sufficient toenable differentiation of an actual pothole event from sensor noise,based on passage of the velocity threshold within the time threshold T1.The ranges of values for the time threshold T1 may be based on datacollected from both potholes and non-pothole ride events. The use ofsuch data to program or “tune” the suspension system facilitates rapiddetection of actual potholes, while helping to minimize negative effectson ride due to increases in damping prompted by “false positive”detections of pothole events.

At block 305, the timer reading T since initialization is compared withthe first predetermined time threshold T1. If the timer reading T isgreater than the value of T1 (i.e., if the time elapsed since there-initialization of the timer is greater than T1), a “true” conditionis recognized and the damping level D is maintained at the referencevalue D1. If the time elapsed since the re-initialization of the timeris less than T1, a “false” condition is recognized and the processproceeds to block 306, where the instantaneous velocity V=Δy/T (i.e.,dy/dt) of the wheel is again calculated.

In block 306, the new calculated value of the instantaneous wheelvelocity V is compared to a second predetermined threshold value Th2. Ifthe new wheel velocity V exceeds Th2, a “true” condition is recognizedand it is determined that the change in wheel position (Δy) over theelapsed time T (i.e., the new instantaneous velocity of the wheel intothe depression) is sufficient to warrant an increase in damping level D.Thus, the process proceeds to block 310. However, if the instantaneouswheel velocity V is equal to or less than Th2, a “false” condition isrecognized and the process proceeds to block 308 where the instantaneouswheel velocity V is re-calculated after passage of an additionalpredetermined time interval Δt (i.e., after T has been incremented byΔt). The process then proceeds back to block 305 to determine if thetotal time T elapsed since initialization of the timer is greater thantime threshold T1. If T is greater than T1, the control routing proceedsback to block 290.

In the manner described above, the loop 305-306-308 repeats as long asthe timer value T does not exceed the threshold T1, and as long as theinstantaneous wheel velocity V does not exceed the velocity thresholdTh2. If the timer value T exceeds the first timer threshold T1 withoutthe wheel velocity V exceeding the velocity threshold VTh2, a “false”condition is recognized and it is determined that the wheel has notmoved or has not moved with sufficient velocity during passage of thetime period T1 to warrant an increase in the damping level D. Thedamping level is thus returned to the initial reference value D1.However, if the wheel velocity V in block 306 exceeds the velocitythreshold Th2 before the timer value T exceeds first timer threshold T1,a “true” condition is recognized and the process proceeds to block 310,where the damping level D is increased by a predetermined amount ΔD to ahigher value of D2. Stated another way, after the passage of every timeinterval Δt, the instantaneous wheel velocity V is re-calculated andboth the timer reading T and the instantaneous wheel velocity V arecompared to respective threshold values to determine whether the dampinglevel D is to be modified. Incremental increases in the damping levelare implemented as a “ramp” or “slope” extending between the initial andnew damping levels. If the instantaneous wheel velocity V exceedsthreshold Th2 within the time period defined by T1, a “true” conditionis recognized and the damping level is increased in block 310. However,if the instantaneous wheel velocity V remains equal to or below thefirst threshold Th2 within the time period defined by T1, the dampinglevel D is thus returned to the initial reference value D1.

The loop formed by blocks 310, 312 and 314 is directed to incrementallyincreasing the damping level by a predetermined amount after the passageof every time interval Δt until either (1) the timer reading T afterinitialization exceeds a second timer threshold T2, or (2) theinstantaneous wheel velocity V exceeds a third velocity threshold Th3.

Instances where the wheel continues to exceed the velocity thresholdswithin the associated time intervals indicate a lack of road support forthe wheel to a depth sufficient to cause the wheel to continue to dropin the “y” direction.

The amounts by which the damping level D is incremented during executionof the control routine described herein may be constant for each step,or the amounts may be determined according to the requirements of aparticular application. The amounts by which the damping level D isincremented may be determined according to the requirements of aparticular suspension system design, the range of damping settingsavailable in a particular type of damping, the method used to actuatethe damping, and other pertinent factors. In addition, the number ofsteps or increments into which the range of damping levels may bedivided to facilitate the incremental increases in damping levels may bedetermined according to the requirements of a particular application.

In block 310, the damping level is increased by a predetermined amountΔD to level D2. The instantaneous wheel velocity V is re-calculatedafter the passage of another time interval Δt (i.e., after timer value Thas been incremented another Δt from its value as used in the previousinstantaneous velocity calculation).

In block 312, the timer reading T is compared with a secondpredetermined time threshold T2. If the timer reading T is greater thanthe value of T2 (i.e., if the time elapsed since the initialization ofthe timer in block 304 is greater than T2), a “true” condition isrecognized and the damping level D is returned to the reference valueD1. However, if the time elapsed since the initialization of the timeris less than T2, a “false” condition is recognized and the processproceeds to block 314.

In block 314, if the instantaneous wheel velocity V is equal to or lessthan threshold Th3, a “false” condition is recognized and the processproceeds back to block 310 where the damping level is again increased bya predetermined amount ΔD and the instantaneous wheel velocity V isre-calculated after passage of an additional predetermined time intervalΔt. The process then proceeds back to block 312 to determine if theelapsed time T is greater than time threshold T2.

In the manner described above, the loop 310-312-314 repeats as long asthe timer value T does not exceed the second timer threshold T2, and aslong as the instantaneous wheel velocity V does not exceed the thirdvelocity threshold Th3. If the timer value T (measured sinceinitialization) exceeds the second timer threshold T2 without the wheelvelocity V exceeding the velocity threshold Th3, a “false” condition isrecognized and it is determined that the wheel has not moved further orhas not moved with sufficient velocity during passage of the time periodT2 to warrant a further increase in the damping level. The damping levelis thus returned to the initial reference value D1.

However, if the wheel velocity V exceeds threshold Th3 prior to thetimer value T exceeding the second timer threshold T2, a “true”condition is recognized and it is determined that the change in wheelposition (Δy) over the elapsed time T (i.e., the speed of the verticalmotion of the wheel into the depression) is sufficient to warrant afurther increase in damping level D to the maximum tuned damping level,D_(MAX) in block 316.

While the process proceeds through the loop defined by blocks310-312-314, the damping level continues to be incremented gradually, instepwise manner so that, if and when the maximum damping level D_(MAX)is required, the increase in damping level from the current dampinglevel to D_(MAX) will be smaller than the increase in damping level fromD1 to D_(MAX). This aids in minimizing or eliminating the “knocking” or“thumping” effect which may be caused by a sudden, large shift inhydraulic pressure needed to progress from D1 to D_(MAX) in a relativelyshorter time period, and which may be discernible by passengers of thevehicle. The process described herein also enables the system dampingforce to be increased incrementally between a first predetermined valueto a next, higher predetermined value. Thus, when it is determined thatthe next, higher predetermined value is required, the size of theremaining increase required to reach the next, higher predeterminedvalue is smaller than the size of the gap between the firstpredetermined value and the highest predetermined value.

In block 320, the damping level is maintained at D=D_(MAX) until theelapsed time as indicated by the timer value T reaches a predeterminedstop point T_(STOP). The damping level is then returned to the initialreference value D1.

By incrementally increasing the damping forces exerted by the dampingresponsive to the continued drop of the wheel into the road depression,the embodiments of the control routine described herein helps tominimize the amount of the damping force increase and delaysimplementation of the force increase for as long as possible, therebypreserving the relatively higher ride quality provided by the lowerdamping level for as long as possible.

Using the embodiments of the control routine described herein,implementation of the damping force increase to D_(MAX) (which has thegreatest deleterious effect on ride quality) is ideally restricted tocases where it is most desired (i.e., cases where the wheel encounters arelatively deep pothole or depression). This increase in damping levellimits the depth to which the wheel drops into the depression and aidsin minimizing the jarring impact caused by the wheel striking theopposite side of the pothole as it rises out of the hole.

A control routine in accordance with an embodiment of the presentdisclosure may be incorporated as a subroutine into a broader new orexisting control routine designed control to additional elements of thesuspension system as well as the active damping mechanism, and/or whichcontrols elements of the active suspension system based on inputs fromboth the wheel position sensors and other types of sensors.

As described above, a control routine in accordance with an embodimentof the present disclosure enables efficient operation of vehiclesuspension systems incorporating continuously variable or multistepsuspension dampers, so as to maximize ride quality and reduce loading onthe suspension system.

As described herein, one embodiment of the present disclosure includesan active vehicle suspension system having an active damping mechanismoperatively coupled to a vehicle wheel and configured for controlling adamping force applied to the wheel responsive to a control signal. Acontroller is operatively coupled to the damping mechanism andconfigured for generating a control signal to the damping mechanismresponsive to a velocity of the wheel in a downward vertical direction.

Also as described herein, another embodiment of the present disclosureprovides a method for controlling a damping level applied to a wheel inan active suspension system. The method includes the steps ofdetermining a velocity defined as a rate of change of a verticalposition of the wheel over a first predetermined time period; comparingthe velocity to a velocity threshold; and where the velocity is greaterthan the velocity-threshold, increasing the damping level.

Also as described herein, another embodiment of the present disclosureprovides a method for applying a damping force to a wheel moving in adownward vertical direction. The method includes the steps of measuringa time during which the wheel moves in the direction; measuring avelocity of the wheel in the direction; comparing the time to athreshold and the velocity to another threshold; and where the time doesnot exceed the threshold and the velocity exceeds the other threshold,applying a maximum available damping force to the wheel.

It will be understood that the foregoing descriptions of embodiments ofthe present disclosure are for illustrative purposes only. As such, thevarious structural and operational features herein disclosed aresusceptible to a number of modifications commensurate with the abilitiesof one of ordinary skill in the art, none of which departs from thescope of the present disclosure as defined in the appended claims.

What is claimed is:
 1. A method of controlling a vehicle suspension fora wheel via a controller, the method comprising: repeatedly calculatinga vertical velocity of the wheel until the vertical velocity exceeds afirst velocity threshold; in response to the vertical velocity exceedingthe first velocity threshold, initiating a timer and maintaining adamping level of an adjustable damping mechanism of the vehiclesuspension at an initial value while repeatedly recalculating thevertical velocity of the wheel until a recalculated vertical velocityexceeds a second velocity threshold; and in response to the recalculatedvertical velocity exceeding the second velocity threshold before thetimer exceeds a first time threshold, sending an adjustment signal tothe adjustable damping mechanism of the vehicle suspension to increasethe damping level of the suspension.
 2. The method of claim 1, whereinsending an adjustment signal to the adjustable damping mechanism of thevehicle suspension to increase the damping level comprises repeatedlysending an adjustment signal to repeatedly increase the damping level ofthe adjustable damping mechanism by an incremental amount.
 3. The methodof claim 2, further comprising recalculating the vertical velocity witheach increase of the damping level of the adjustable damping mechanismby the incremental amount, wherein the repeatedly sending an adjustmentsignal to repeatedly increase the damping level is performed until therecalculated vertical velocity exceeds a third velocity threshold or thetimer exceeds a second time threshold.
 4. The method of claim 3, whereinthe second time threshold is greater than the first time threshold. 5.The method of claim 3, wherein the sending an adjustment signal to theadjustable damping mechanism to increase the damping level comprises, inresponse to the recalculated vertical velocity exceeding the thirdvelocity threshold, sending an adjustment signal to the adjustabledamping mechanism to increase the damping to a maximum level.
 6. Themethod of claim 3, further comprising, in response to the recalculatedvertical velocity being less than the third velocity threshold and thetimer exceeding the second time threshold, sending an adjustment signalto the adjustable damping mechanism to revert the damping level of theadjustable damping mechanism of the vehicle suspension to the initialvalue.
 7. The method of claim 1, further comprising, in response to therecalculated vertical velocity being less than the second velocitythreshold and the timer exceeding the first time threshold, maintainingthe damping level of the adjustable damping mechanism of the vehiclesuspension at the initial value.
 8. The method of claim 1, wherein thevertical velocities of the wheel are calculated by taking timederivatives of respective vertical positions of the wheel, said verticalpositions being measured by one or more sensors.
 9. The method of claim1, wherein the adjustable damping mechanism comprises a variableorifice, and wherein the sending the adjustment signal includessignaling a change in a size of the variable orifice to provide acorresponding change in damping level for the vehicle suspension. 10.The method of claim 9, wherein the sending the adjustment signal to theadjustable damping mechanism comprises using a stepper motor to alterthe size of the variable orifice.
 11. The method of claim 1, wherein thesending an adjustment signal to the adjustable damping mechanism toincrease the damping for the vehicle suspension causes a change in aphysical aspect of the damping mechanism to provide a correspondingchange in damping level for the vehicle suspension.
 12. A vehiclesuspension system, comprising: an active damping mechanism operativelycoupled to a vehicle wheel and configured to control damping applied tothe wheel; and a controller operatively coupled to the active dampingmechanism, the controller being configured to: repeatedly calculate avertical velocity of the wheel until the vertical velocity exceeds afirst velocity threshold; in response to the vertical velocity exceedingthe first velocity threshold, initiate a timer and maintain a dampinglevel of the active damping mechanism at an initial value of dampingwhile repeatedly recalculating the vertical velocity of the wheel untila recalculated vertical velocity exceeds a second velocity threshold;and in response to the recalculated vertical velocity exceeding thesecond velocity threshold before the timer exceeds a first timethreshold, adjust the active damping mechanism to increase the dampinglevel applied to the wheel.
 13. The system of claim 12, wherein thecontroller is configured to adjust the active damping mechanism toincrease the damping level by repeatedly increasing the damping level byan incremental amount.
 14. The system of claim 13, wherein thecontroller is configured to: recalculate the vertical velocity with eachincrease of the damping level by the incremental amount; and adjust theactive damping mechanism to repeatedly increase the damping by theincremental amount until the recalculated vertical velocity exceeds athird velocity threshold or the timer exceeds a second time threshold.15. The system of claim 14, wherein the controller is further configuredto, in response to the recalculated vertical velocity exceeding thethird velocity threshold, adjust the active damping mechanism toincrease the damping to a maximum level.
 16. The system of claim 14,wherein the controller is further configured to, in response to therecalculated vertical velocity being less than the third velocitythreshold and the timer exceeding the second time threshold, adjust theactive damping mechanism to revert to the initial value of damping. 17.The system of claim 12, wherein the controller is further configured to,in response to the recalculated vertical velocity being less than thesecond velocity threshold and the timer exceeding the first timethreshold, control the active damping mechanism to maintain the initialvalue of damping.
 18. The system of claim 12, further comprising one ormore sensors that measure a vertical position of the wheel, wherein thecontroller is configured to calculate the vertical velocities by takingtime derivatives of respective vertical position measurements from theone or more sensors.
 19. The system of claim 12, wherein the activedamping mechanism comprises a variable orifice, a size of the variableorifice corresponds to a value of damping provided by the active dampingmechanism, and the controller is configured to control the size of thevariable orifice.
 20. The system of claim 12, wherein the active dampingmechanism comprises at least one of a variable orifice, a hydraulicallyactuated cylinder, a cylinder actuated by a solenoid valve, anelectromagnetically energized proportional-action valve, and amagneto-rheological fluid.